1. Field of the Invention
The present invention relates to a method of adjusting a slice thickness in a nuclear magnetic resonance imaging.
2. Description of the Background Art
In a nuclear magnetic resonance imaging apparatus, it has been considered desirable to make a thickness of a slicing plane as thin as possible, in order to improve the resolution.
Conventionally, the slice thickness has been made thinner by using a greater gradient magnetic field strength, or by using a longer period for applying excitation pulses, or by using a three-dimensional Fourier transform (3DFT) method.
However, in order to provide the greater gradient magnetic field strength, it is necessary to use a gradient magnetic field generation device of a larger capacity. Thus, this is rather expensive manner for obtaining a thin slice thickness.
On the other hand, when the longer period is used for applying excitation pulses, a period for echo generation also becomes longer, and this in turn produces a severe limitation in obtaining T1 (longitudinal relaxation time) emphasized images or T2 (transverse relaxation time) emphasized images.
As for 3DFT, there is a limitation that the signal collection period is longer, so that scanning with a long repetition time is practically impossible, and consequently it is difficult to obtain the T2 emphasized images.